This PR provides implementation of ticker_free() function for the following boards:
ARCH_PRO
EV_COG_AD3029LZ
EV_COG_AD4050LZ
K22F
K64F
K82F
KW24D
KW41Z
LPC546XX
NRF51_DK
NRF52_DK
NUCLEO_F207ZG
NUCLEO_F401RE
NUCLEO_F429ZI
NUCLEO_F746ZG
REALTEK_RTL8195AM
Set the second highest user level, leaving the highest for UART (we are having constant overflows) and two levels below for everything else.
This should increase the timer accuracy.
RTC counter is 24-bit. Upper layer handles counter size and wraps ticks count when interrupt is to be fired before passing it to common_rtc_set_interrupt(), but for consistency and safety reasons we can wrap it again in the NRF driver.